This article gives a lot of ideas, from obvious choices (Samantha Bee, Jessica Williams, Brian Williams), to veteran comedians who would seem pretty hard to get at this point (Chris Rock, Al Franken). As long as we're considering the latter, how about Steve Carell, Tina Fey, or Alec Baldwin?
The article as a whole is disappointing — I was hoping to see some analysis of who would actually be good at doing what Jon Stewart does. Instead, it's just a list of available funny people. The new host needs to be not just someone who can tells jokes about the news from cue cards and make some funny faces in between, but also someone with the gravitas to sit down face-to-face with the Secretary of Defense or Secretary of State and ask hard-hitting questions.
"SamanthaBeeFeb2011" by Justin Hoch. Licensed under CC BY 2.0 via Wikimedia Commons.
UPDATE: Jessica Williams has taken herself out of the running:
I'm not hosting. Thank you but I am extremely under-qualified for the job! At this age (25) if something happens politically that I don't agree with, I need to go to my room & like not come out for, like, 7 days.